A new AIDS vaccine that is used to treat the disease is able to suppress the virus for at least one year, say researchers of a small trial.

You can read about this preliminary study in Nature Medicine. It is being called the first demonstration of an efficient therapeutic vaccine against AIDS.

18 volunteers were involved in the trial. They were all infected with HIV. The trial was carried out in Brazil. None of the volunteers had been taking antiviral drugs. Four months after taking the experimental vaccine their levels of HIV (in the bloodstream) had gone down 80%.

8 of the volunteers experienced a 90% drop of the HIV in their bloodstream - four of them had much lower levels.

This new vaccine has the potential of keeping infected patients healthy. It could be a good alternative to the present combination of drugs people have to take.

The plan with this new vaccine is to give a patient one injection a year. This should be enough to stop the infection from becoming a problem.

This investigation was carried out by Dr Jean-Marie Andrieu, Institute of Research for Vaccines and Immunotherapies for Cancer and AIDS, Paris, France.

Researchers said the only detectable side-effect is a painless swelling of the lymph nodes. They say the lymph node swelling shows that the immune system has been kicked into action.

They could not explain why the vaccine did not work for everyone. They said further studies were needed.